Florida Agricultural Experiment Stations


 Foliage samples were collected between July 25 and August
11, 1955. Five leaves per tree were taken at random from the
middle of non-fruiting spring-flush twigs, making a total of 100
leaves for each composite sample. Each sample was washed
or scrubbed with cheesecloth, depending on the amount of foreign
material on the leaves, in a 2.5 percent neutral detergent. The
leaves were then rinsed three times with tap water and once
with deionized water. After the samples had been air dried,
they were placed in an oven at approximately 70' C. for not less
than 48 hours. A Wiley mill was used to grind the leaves and
the ground material was stored in air-tight jars.
 Soil samples were collected at the same time as leaf samples.
One core was taken to a depth of six inches just outside the leaf
drip and on the same side of each tree from which leaves were
taken. Twenty cores made a complete sample. The samples
were air dried, screened through a sieve with openings about
one-eighth inch in diameter and then thoroughly mixed.
 Fruit samples were collected between March 12 and March
20, 1956, and totaled 161 samples from 155 groves. The fruit
crop was harvested before samples could be taken in 13 of the
groves. Four fruits were picked at random from each of the 20
trees, making a total of 80 fruits for each sample. Fruits of late
bloom were avoided. Fruits were washed and measured for ex-
ternal qualities. Each sample was then randomly divided into
two equal subsamples. One subsample was analyzed for min-
eral composition and the other for juice quality.
 For study of mineral composition one subsample was ground
in a comminuting machine through a quarter-inch screen. To
determine the moisture content, approximately 50 grams of the
comminuted material was weighed into an evaporating dish and
dried in an oven at 60 C. for not less than 96 hours and re-
weighed. A second portion of about 500 grams of the com-
minuted material was first dried in an oven at 600 C., then ground
in a Wiley mill and stored in an air-tight jar.

 METHODS OF ANALYSIS
 Mineral Composition of Leaves and Fruits.-Except for total
nitrogen, the samples were digested in 100 ml. volumetric flasks
with an acid solution containing 1 part of 60 percent perchloric
acid to 4 parts of nitric acid. Nitrogen was measured by means.
of the "semi-micro Kjeldahl procedure" (29), and phosphorus
by ammonium molybdate and amino-naphthol-sulfonic acid